If time outs occur on a page you should at the very least provide a warning of how long a user has to complete an activity. If possible, offer users a way to extend how long they have. You should aim to have no functions which require time outs. A person with a physical disability accessing the internet will take a lot longer to tab through a page or to fill out a form or complete an action than someone without a disability who has use of a mouse. Many users with disabilities will have only one-button access or may control their computer through use of a switch or a puff and sip device. Navigating like this takes a great deal of time and effort. If a page times out on a user halfway through filling out a form they will find it impossible to use your site.

Read about how Time Outs criterion scoring works.